This disclosure relates generally to systems and methods for monitoring of structures, and more particularly, to systems and methods for continuously monitoring structures, e.g., pipes and vessels, for defects such as wall thinning caused by corrosion.
The petroleum and chemical industry has been searching for a means to monitor the condition of piping and vessels in facilities used for a variety of product flow and product processing. During the normal operation of these facilities, corrosion and erosion occur as a result of various products flowing through pipes and vessels and lead to a thinning of the pipes' and vessels' walls. The result of this wall thinning can range from loss of production, due to pipe leaks, to catastrophic failures which present safety and property damage issues. The operating conditions of the piping and vessels ranges from ambient temperatures of the surrounding environment (−40 F to 120 F) to very elevated temperatures (1000 F). With this range of operating conditions, the industry has been actively searching for technologies that would allow for online monitoring of the conditions of the components in order to either mitigate the corrosion through chemical treatment or alert the plant operators of a serious condition that would require immediate attention.
The current technology to address the issue of corrosion in piping and vessel wall material includes ultrasonic wall thickness measurement, X-ray imaging of the pipe or vessel, visual inspection of the pipe or vessel as well as potential drop measurements. Ultrasonic, X-ray and visual inspection techniques often require the systems to be taken out of service or to be inoperative for a period of time to allow for the inspection process to be completed. The potential drop measurement systems currently available on the market allow for online measurements but are limited in their capability to detect the effects of corrosion in piping and vessel wall material. For example, conventional potential drop measurement systems do not have sufficient sensitivity for detecting low rates of corrosion due to noise generated from sequentially multiplexing various test points.
Other online measurement systems such as product sampling for corrosion products in the material flowing in the pipe or vessel have also been employed. These are sampling techniques that have limited value due to low volume of corrosion byproducts flowing with the desired fluids in pipes and vessels. These techniques are adequate for the detection of general corrosion where a greater concentration of corrosion byproducts are found in the fluid stream within pipes and vessels but these techniques are not applicable for the detection of local pitting which only introduces a small volume of corrosion byproduct in the fluid stream within the pipe of vessel.
Therefore, a need for techniques to monitor structures, e.g., pipes and vessels, for defects with little or no disruption to the operation of the facilities including such structures.